1. Field of the Invention
The invention relates to an electrochemical storage cell or battery of the alkali metal and chalcogen type with at least one anode space for receiving the anolyte, and a cathode space for receiving the catholyte, which are separated from each other by an alkali ion-conducting solid electrolyte wall.
2. Description of the Prior Art
Such rechargeable electrochemical storage cells with a solid electrolyte are highly suitable for constructing storage batteries with higher energy and power density. The solid electrolyte or .beta.-aluminum oxide used, for instance, in sodium-sulfur storage cells, allows only sodium ions to pass. This means that, contrary to lead storage cells, practically no self-discharge takes place and no secondary reactions occur during the discharge such as, for instance, water dissociation in the case of lead/lead oxide systems. The current yield, i.e. the Faraday efficiency of a sodium/sulfur storage cell is close to 100%.
In these storage cells it is an important disadvantage that the alkali metal can be filled into the anode space of the storage cells only at considerable technical costs. Filling-in the alkali metal raises problems particularly for the reason that the alkali metal, preferably sodium, is filled into the anode space of the storage cells. The sodium must be filled into the anode space in a vacuum or in a protective gas. The filled anode space must, likewise, be sealed off under vacuum conditions or in a protective gas. Sodium, as is well known, is a strongly electronegative metal which has a very large capacity for reduction so that it is heavily oxidized by the air oxygen, especially by moist air. Oxygen must not be present in any case within the cell because the electrical behavior is degraded thereby. This causes in particular an increase of the resistance through the formation of a high-resistance Na.sub.2 O-layer on the solid electrolyte. Furthermore, the corrosive action of the oxygen-containing sodium on metallic cell components, in particular on the seal and on the connecting glass between the .alpha. and .beta.-aluminum oxide is increased by oxygen present within the cell. Such bound oxygen in the moisture and in Na.sub.2 O and free oxygen in the anode space have, as explained above, a detrimental effect and are designated detrimental bound or free oxygen.